Aircraft arresting device with centrifugal brake

ABSTRACT

An aircraft-arresting device includes a tape reel and a brake for retarding rotation of the reel. The brake includes a rotor and a stator having cooperating braking means thereon. A centrifugally operated brake actuating means is mounted on the rotor for rotation therewith to engage the braking means with a force proportional to the square of the reel velocity. The centrifugally operated brake-actuating means may include a cylinder mounted on the reel and a piston shiftably mounted in the cylinder. Rotation of the reel causes shifting of the piston due to centrifugal force to apply hydraulic pressure to hydraulic brake cylinders with a force which is proportional to the square of the reel velocity. The braking device may include a static brake-applying means for engaging the braking means when the rotor is at rest in order to hold a tape under tension. The static brake-applying means is responsive to rotation of the reel to move to a brake-disengaging position. Locking means may be provided for holding the static brake-applying means in a brakedisengaging position once the reel begins to rotate.

United States Patent [21 1 App]. N0 [22] Filed {45] Patented [73] Assignee [54] AIRCRAFT ARRESTING DEVICE WITH CENTRIFUGAL BRAKE 9 Claims, 4 Drawing Figs.

[52] US. Cl 188/187, 244/1 10 [51] lnt.Cl B60tll/10 [50] Field ofSearch 188/103,

[56] References Cited UNITED STATES PATENTS 2,084,244 6/1937 Critz l88/183UX 2,406,156 8/1946 Nardone... 188/180 2,426,967 9/1947 Evans... 188/180X 2,451,373 10/1948 Beall 188/180X Primary ExaminerMi1t0n Buchler Assistant Examiner-Paul E. Sauberer AlmrneyMeyer, Tilberry and Body ABSTRACT: An aircraft-arresting device includes a tape reel and a brake for retarding rotation of the reel. The brake includes a rotor and a stator having cooperating braking means thereon. A centrifugally operated brake actuating means is mounted on the rotor for rotation therewith to engage the braking means with a force proportional to the square of the reel velocity. The centrifugally operated brake-actuating means may include a cylinder mounted on the reel and a piston shiftably mounted in the cylinder. Rotation of the reel causes shifting of the piston due to centrifugal force to apply hydraulic pressure to hydraulic brake cylinders with a force which is proportional to the square of the reel velocity. The braking device may include a static brake-applying means for engaging the braking means when the rotor is at rest in order to hold a tape under tension. The static brake-applying means is responsive to rotation of the reel to move to a brake-disengaging position. Locking means may be provided for holding the static brake-applying means in a brake-disengaging position once the reel begins to rotate.

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ATTOR NEYS AIRCRAFT ARRESTING DEVICE WITH CENTRIFUGAL BRAKE BACKGROUND OF THE INVENTION This application pertains to the art of braking and more particularly to centrifugally actuated braking. The invention is particularly applicable to aircraft-arresting gear brakes and will be described with particular reference thereto although it will be appreciated that the invention has broader applications in other devices requiring brakes.

A well-known type of aircraft-arresting device includes a rotatable reel having an elongated flat tape wound thereon. The tape is attached to a cable stretched across an aircraft runway. An aircraft landing on the runway engages the cable and pulls on the tape so that the reel rotates and the tape is unwound from the reel. The reel is usually braked by a braking device in order to apply a retarding force to rotation of the reel and bring the aircraft to a stop.

One previous manner of applying a braking force to the reel in such a device has been to drive an hydraulic pump from the rotating reel as the tape is unwound therefrom. Such arrangements are disclosed in US. Pat. No. 3,142,458 to Byrne et al. and in copending U.S. application Ser. No. 689,713 filed Dec. 1 1, 1967. In such prior arrangements, a mechanical drive system is required for operating the pump, and control valves must be arranged to obtain the desired pressure from the pump. Such arrangements are rather complex and expensive to construct and maintain. In addition, pumps are often subject to leakage and wear which sometimes renders the device unsafe and requires constant maintenance.

In aircraft-arresting devices of the type described, the flat tape is wound upon the reel in concentric layers. In this manner, the reel is rotated at a substantially constant rate when an aircraft is arrested. For example, in a theoretical system the circumference of the outer most layer of tape on a wound up reel may be feet or 3.05 meters. When an aircraft engages the cable to pull tape from the reel, a linear movement of the aircraft a distance of 10 feet or 3.05 meters along the runway will rotate the reel substantially one revolution and IOfeet or'3.05 meters of tape will be unwound from the reel. In this 10 feet or 3.05 meters of linear travel of the aircraft, the aircraft speed may be an average of 10 feet per second. In such a situation, the reel would be rotated at one revolution per second. As the aircraft continues moving down the runway it is braked by the braking means which retards rotation of the reel and is moving at a slower rate. At a later point in time, the aircraft may be movingat an average speed of only 8 feet or 2.5 meters per second. However, due to the fact that tape has been unwound from the reel the circumference of the outer most layer of tape on the reel will also be 8 feet or 2.5 meters. Therefore, movement of the aircraft at a later time at an average rate of 8 feet or 2.5 meters in one second will also unwind 8 feet or 2.5 meters of tape from the reel and rotate the reel substantially one revolution so that the reel velocity is still I revolution per second. Prior devices have used rather complex valve arrangements in order to make the braking resistance proportional the reel velocity so that the aircraft is arrested at a uniform deceleration rate.

It would be desirable to have a braking system arranged so that the braking force was proportional to the angular velocity of the reel while eliminating many of the moving parts such as pumps and control valves of prior devices.

SUMMARY OF THE INVENTION An aircraft-arresting device includes a rotatable tape reel anchored at an edge of an aircraft runway or landing strip. The reel has an elongated flat tape wound thereon in ever increasing layers and the tape has a free end connected to a cable which is stretched across the landing strip. An aircraft landing on the landing strip engages the cable and pulls on the tape to cause rotation of the reel and unwinding of the tape from the reel. The reel is provided with a braking device to retard rotation which places a tension in the tape and brings the aircraft to a stop. The braking device is centrifugally operated under the action of centrifugal force caused by rotation of the reel. The centrifugal force acting in the braking device varies in accordance with the angular velocity of the reel and the braking force also varies in accordance with the angular velocity of the reel.

In a preferred arrangement, the centrifugal-braking device includes a cylinder mounted radially on the motor of the brake. The outer end of the cylinder is connected to a hydraulic line which leads to a plurality of brake cylinders on the braking device. A piston is slideably mounted in the cylinder and the piston moves toward the outer end of the cylinder under the action of centrifugal force when the rotor is rotated. The piston acts against hydraulic fluid in the outer end of the cylinder to transmit hydraulic pressure through the hydraulic line to the brake cylinders for engaging the brakes. The force with which the piston pushes against the hydraulic fluid varies in accordance with the angular velocity of the reel because the centrifugal force acting on the piston varies with the angular velocity of the reel.

In one arrangement, the braking device may include static brake-applying means which is biased to a brake-engaging position when the rotor is at rest. Initial rotation of the rotor may move the static brake applying means to a brake disengaged position.

It is a principal object of the present invention to provide an aircraft-arresting gear with a braking device which is simple in operation and very economical to manufacture and maintain.

It is another object of the present invention to provide such a braking device which is centrifugally operated and varies the braking force in accordance with the square of the angular velocity of a brake rotor.

It is also an object of the present invention to provide a braking device which is centrifugally operated and applies a variable hydraulic pressure to a brake cylinder in proportion to the angular speed of a brake rotor.

It is an additional object of the present invention to provide a braking device with a static brake applying means which is biased to a brake-engaging position when a brake rotor is at rest and automatically moves to a brake-disengaged position when the rotor begins to rotate.

It is a further object of the present invention to provide such a static-braking means with a lockout for locking it in a brakedisengaged position once rotation of the brake rotor begins.

BRIEF DESCRIPTION OF THE DRAWING The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof.

FIG. I is a plan view of an aircraft-arresting gear mounted adjacent an aircraft-landing strip and having the braking device of the present invention incorporated therein;

FIG. 2 is a side cross-sectional elevational view taken on line 22 of FIG. 1;

FIG. 3 is a cross-sectional elevational view taken on line 3-3 of FIG. 2; and

FIG. 4 is a cross-sectional elevational view of a modified centrifugal brake cylinder and piston for use with the braking device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, wherein the showings are for purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting same, FIG. I shows arresting devices A and B positioned on opposite sides of an aircraft-landing strip C. Arresting device A may be the same as arresting device B and only arresting device B will be described in some detail. Each arresting device may be anchored to a concrete foundation as shown at I2 for arresting device B. As shown in FIG. I, arresting device B has a rotatable reel 14 on which an elongated flat tape 16 is wound in ever increasing layers or coils. Reel 14 is rotatable relative to a substantially horizontal supporting shaft which is secured to supporting blocks 18 and 20. Arresting device A is similarly constructed and has an elongated flat tape 22. Tapes 16 and 22 may be trained through stationary sheaves D and E respectively which serve as guides for the tapes as they are being unwound from the reels. Tapes 16 and 22 are also trained through sheave assemblies G and H which are secured to opposite sides of landing strip C. Sheaves G and H have pairs of pulleys or cylinders 24, 26, 28 and 30 rotatably mounted on substantially vertical axes. Tapes 16 and 22 are trained through the pulleys on sheaves G and H and connected by joint means 34 and 36 to a cable .1 which is stretched across landing strip C. As shown in FIG. 1, an aircraft K landing on landing strip C moves into engagement with cable J and moves to the shadow line position while dragging cable J along with it. Movement of aircraft K and cable .I to the shadow line position as shown in FIG. 1 causes rotation of reel 14 and unwinds tapes 16 and 22 from their respective reels. Each arresting device may have a motor M drivingly connected with reel 14 through a driving chain 40 or the like for turning reel 14 in a reverse direction to coil tapes 16 and 22 back on the reels after an aircraft has been arrested.

As shown in FIG. 3, reel 14 includes sideboards 46 and 48 between which tape 16 is coiled. Sideboards 46 and 48 may be welded or otherwise secured to a rotor R of a braking device. Rotor R includes a peripheral portion 50 and side elements 52 and 54. Side elements 52 and 54 of rotor R are rotatably supported on shaft P by bearings 56 and 58. Shaft P is nonrotatably secured at its ends 60 and 62 to blocks 18 and by suitable keys or fastening means 64 and 66.

Attached to the inner periphery of peripheral portion 50 of rotor R are a plurality of rotor brake elements only one of which is indicated by a numeral 70. Each rotor brake element such as 70 has brake pad elements 72 and 74 secured to opposite sides thereof. The outer periphery of rotor brake element 70 is notched at circumferentially spaced intervals to receive circumferentially spaced keys as at 80 which extend axially of rotor R. In this manner, rotor brake elements 70, along with brake pads 72 and 74, are shiftable axially of rotor R.

Shaft P includes'a central circular portion defining a stator S of the braking device. The stator has a plurality of stator brake elements only one of which is indicated by numeral 80. Stator brake element 80 has brake pads 82 and 84 secured to the sides thereof. Each stator brake element 80 is also notched at circumferential intervals to receive circumferentially spaced keys as at 86 which extend axially of stator S. It will be seen that when reel 14 and rotor R are rotated the rotation may be retarded by applying a squeezing force to the rotor and stator brake elements so that there will be a frictional braking force as between brake pads 74 and 82.

The above-described brake itself forms no part of the present invention and details of this general type of brake may be found in such prior U.S. Pats. as Martin No. 2,683,504; Albright No. 2,826,274; Albright No. 2,885,033; and Strance No. 3,309,043.

As shown in FIGS. 2 and 3, peripheral portion 50 of rotor R has a plurality of fluid pressure means defined by hydraulic brake cylinders secured thereto as at 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110 and 112. The other side of peripheral portion 50 or rotor R may have a similarly arranged group of hydraulic brake cylinders and only two of which are shown at 114 and 116 in FIG. 3. From FIG. 3 it will be seen that when hydraulic pressure is supplied to the brake cylinder they apply forces acting towards each other to squeeze the rotor and rotor brake elements 70 and 80 toward one another for providing a frictional retarding force between the brake pads as at 72 and 82. A brake-actuating means may be defined by a conventional hydraulic cylinder T cast integrally with peripheral portion 50 of rotor R, or it may be a standard hydraulic cylinder secured to rotor R or a sideboard of reel 14 by welding or bolting. Cylinder T includes an elongated cylindrical internal bore 120 which extends radially from the rotational axes of rotor R as shown in FIG. 2. Bore 120 may be closed at its outer end by a plate 122 secured to cylinder T as by bolts 124 and 126. A piston Y is slideably received in bore 120 of cylinder T. Piston Y may have a suitable conventional sealing ring for sealing against the walls of bore 120. The outer end of bore 120 outwardly of piston Y is filled with a suitable hydraulic fluid 132. A hydraulic line 134 communicates with bore 120 at the outer end thereof which is filled with hydraulic fluid 132. Hydraulic line 134 communicates through branch hydraulic lines 140, 142, 144, 146, 148, 150, 152, 154 and 156 with hydraulic brake cylinders 92, 94, 96, 100, 102, 104, 108, 110 and 112 respectively. The inner end of hydraulic cylinder T may have a hole 160 communicating with bore 120 to allow ingress and egress of air on the backside of piston Y.

When an aircraft K lands on landing strip C and engages cable .I to pull tape 16 from reel 14, reel 14 and rotor R begin to rotate. This creates a centrifugal force acting on piston Y in cylinder T which tends to move piston Y outwardly in bore 120. The centrifugal force acting on piston Y and causing it to move outwardly is represented by the equation Mrw where M is the mass of piston Y, r is the distance from the axis of rotation of rotor R to the center mass of piston Y, and w is the square of the angular velocity of rotor R in radians per second. Therefore, the centrifugal force tending to move piston Y outwardly in bore 120 varies in accordance with the square of the angular velocity of rotor R. As rotor R rotates, the outer flat end of piston Y presses against hydraulic fluid 132 and forces it through hydraulic line 134 to branch lines 140l56 communicating with the fluid pressure means or hydraulic brake cylinders as previously described. As the angular velocity of rotor R increases, flattened outer surface 170 of piston Y will be pressed against hydraulic fluid 132 with increasing force and this will also increase the engagement force between rotor and stator brake elements 70 and 80. In this manner, the braking force applied to retard rotation of reel 14 automatically varies in a desirable fashion to apply a constant braking force when reel 14 rotates at a constant angular velocity and to automatically increase or decrease the braking force as the rotation of reel 14 speeds up or slows down.

As previously described, a motor M is provided to drive a chain 40 for rotating reel 14 in an opposite direction to coil tape 16 back on reel 14 after an aircraft has been arrested. Chain 40 drives a sprocket in FIG. 2 and 3 which is rotatably mounted on shaft P by bearing 182. Sprocket 180 may include a manual lever 184 for moving a clutching device 186 into engagement with a cooperating clutching device 188 on rotor R. In this manner, clutching devices 186 and 188 may be selectively engaged by means of lever 184 to rotate rotor R and reel 14 in the proper direction to coil tape 16 back on reel 14 by means of motor M. In a like manner, lever 184 may be used to disengage clutching devices 186 and 188 when the tape is completely wound back upon the reel.

Once a tape is wound back upon a reel, it is desired to keep cable .I tightly stretched across landing strip C so that it will not fall slack and be passed over by the engaging hook on aircraft K. In order to keep cable I tightly stretched across landing strip C, it is necessary to somehow hold reel 14 against rotation. One manner of doing this would be to leave clutching devices 186 and 188 engaged so that the resistance to rotation of motor M would also prevent rotation of reel 14. However, arrestment of an aircraft would then cause rotation of motor M in a reverse direction and cause unnecessary wear and possible damage to both motor M and clutching devices 186 and 188. Therefore, the present invention includes a static brake-applying means for holding reel 14 against rotation when cable] is stretched tightly across landing strip C.

As shown in FIGS. 2 and 3, a manually operated valve 190 may be provided in hydraulic line 134 to prevent hydraulic fluid 132 from traveling through line 134 to engage the brakes when the reel is being rotated in a windup direction by rewind motor M.

In accordance with the present invention, a static brake-applying means is provided to engage the braking means when rotor R and reel 14 are at rest, in order to keep cable J tightly stretched across landing strip C. The static brake-applying means includes a second hydraulic cylinder 202 which may be welded or bolted by brackets 204 and 206 to the outer periphery or peripheral portion 50 of rotor R as shown in FIG. 3. In the arrangement shown, bolts 208 and 210 are used to secure the brackets in place. It will be understood that second hydraulic cylinder 202 could also be welded or otherwise secured to a sideboard 48 of reel 14. Cylinder 202 includes an inner cylindrical bore 212 slideably receiving a piston 220 which may have a circumferential sealing ring 222 thereon for sealing engagement with the wall of bore 212. One end of cylinder 202 threadedly receives a bolt 224 which has a bearing plate 226 on its and within bore 212. A coil compression spring 228 is positioned within bore 212 between bearing plate 226 and piston 220. Rotation of threaded bore 224 will move bearing plate 226 axially within bore 212 to vary the compression force of spring 228 tending to shift piston 220 to the right as viewed in FIG. 2. The other end of cylinder 202 may be closed by a plate 230 secured to cylinder 202 as'by bolts 232 and 234. An air bleed 251 may be provided in cylinder 202 rearwardly-of piston 220. Hydraulic fluid 240 within bore 212 of cylinder 202 communicates with hydraulic line 242 having branch lines 244 and 246 containing valves 248 and 250. In addition, lines 244 and 246 communicate with a main hydraulic line 258 which in turn communicates with branch hydraulic lines 260, 262 and 264 connected respectively with hydraulic brake cylinders 90, 98 and 106.

Valve 248 is preferably a one-way ball check valve having a ball spring biased against a seat to normally prevent flow of fluid from cylinder 202 through lines 244 to line 258. The spring bias against the ball in valve 248 is preferably great enough to prevent the ball from moving away from the seat under centrifugal force when rotor R and reel 14 are rotated. Valve 250 is a manual valve which may be manually opened or closed so that fluid flow from line 246 to line 258 may be permitted or prevented. In operation of the static brake applying means, valve 250is manually opened to allow flow of hydraulic fluid 240 through lines 242, 246, 258 and branch lines 260, 262 and 264. Bolt 224 may be adjusted so that piston 220 applies the desired amount of force on hydraulic fluid 240 to activate brake cylinders 90, 98 and 106 to engage the brake pads of brake elements 70 and 80. All this is done when reel 14 and rotor R are at rest and tape 16 is completely wound upon reel 14. Manual valve 250 is then closed. This operation of cylinder 202 prevents rotation of reel 14 and rotor R when cable .I is stretched tightly across landing strip C. Once an aircraft engages cable .I and begins pulling tape 16 from reel 14, reel 14 begins to rotate clockwise as viewed in FIG. 2 and the inertia or resistance to movement of piston 220 with reel 14 will cause piston 220 to move to the left in FIG. 2 against the bias of spring 228. This movement will relieve pressure forwardly of piston 220 in bore 212 and also relieve pressure in brake cylinders 90, 98 and 106 through one-way check valve 248. After a period of time piston 220 will be rotating at the same speed as reel 14 but pressure cannot be transmitted from bore 212 back into brake cylinders 90, 98 and 106 because manual valve 250 is closed and check valve 248 prevents such pressure transmission. Once an aircraft has been arrested and reel 14 is stopped, hydraulic pressure will be relieved in cylinder T, and valve 190 in hydraulic line 134 may be closed. Motor M is then started to turn reel 14 in a reverse direction to wind tape 16' back upon reel 14. Once the tape is rewound, valve 190 is again open to ready the centrifugal braking device for another arrestment. In addition, manual valve 250 is opened so that hydraulic fluid may again flow into cylinders 90, 98 and 106 to apply the static-braking force. Manual valve 250 is then closed so that the system is in readiness for another arrestment of an aircraft.

FIG. 4 shows a modification of centrifugal-braking cylinder T for varying the amount of force produced on the piston within the cylinder. In this embodiment, a cylindrical insert 302 is threaded within bore asat 304. Insert 302 includes a central cylindrical bore 306 which contains hydraulic fluid 132 and communicates with hydraulic line 134 through an opening 308. A small diameter piston element 310 is slideably received within bore 306 and sealed by a sealing ring 312. The upper end of piston 310 is formed with a threaded shank 314 which is threadedly engaged in a threaded bore 316 in a large diameter piston element 320 slideably received in bore 120. An additional air bleed 322 may be provided in the wall of cylinder T between pistons 310 and 320. Also, a stop 324 may be defined by a bolt threaded through the wall of cylinder T bear against the upper end of piston 320 for preventing piston 310 from completely leaving bore 306. With this arrangement, piston 320 may be of various lengths or even of various materials of different weights so that the braking force produced can be varied in accordance with the mass of an aircraft being arrested. The centrifugal force acting upon the piston, as previously described, is equal to Mrw so that varying the mass of pistons 320 will also vary the centrifugal force on it and this in turn will vary the pressure supplied to the hydraulic cylinders for braking reel 14. For example, for a given angular velocity of reel 14, the pressure supplied to the hydraulic cylinders may be doubled by doubling the mass of piston 320 which in turn will double the centrifugal force tending to shift piston 320 o'utwardly in cylinder T. Instead of providing an adjustable mass as shown in the manner illustrated in FIG. 4, it is also possible to substitute different length pistons Y in the cylinder of FIG. 3 and also to change the mass of piston Y by using different materials or by boring holes in the backside of piston Y to reduce its mass.

It will be understood that two or more centrifugal braking cylinders T may be provided and that they may be provided on both sides of reel 14 and rotor R. It is also possible to provide more than one static brake-applying device 202 if so desired. In a preferred arrangement, there are two centrifugal brake cylinders T arranged on opposite sides of rotor R to dynamically balance rotor R. In the above-described device, it will be noted that centrifugal-braking device T will provide very little braking force when reel 14 is rotating at a very low angular velocity. This is no problem because it is common to abruptly arrest an aircraft when tape 16 is completely run off of reel 14 as by that time the aircraft if moving at a very low velocity. However, it is possible, if so desired, to provide a static braking device such as 202 with valves such as 248 and 250 omitted. In such an arrangement, with reel 14 at rest and tape 16 completely wound upon reel 14, bolt 224 may be manually tightened in order to sufficiently bias piston 220 against hydraulic fluid 240 and apply a braking force to some of the hydraulic-braking cylinders. This braking force may be initially reduced slightly when rotation of reel 14 begins but would be reapplied when piston 220 came up to the rotational speed of reel 14. Therefore, a predetermined static-braking force would be applied to reel 14 independent of centrifugalbraking device T throughout the entire arrestment of an aircraft. At the end of an arrestment, bolt 224 could be loosened to remove all biasing force on piston 220 by spring 228 so that the brakes would be disengaged and reel 14 could be reversely rotated by motor M. Obviously, other mechanical-braking devices could be used for this purpose. It will also be understood that it is possible to combine the present braking system with certain features of the earlier mentioned US. Pat. to Byrne et al. No. 3,142,458 and with other devices if so desired.

It will be understood that in a preferred arrangement reel 14 may be rotatable on a substantially vertical axis rather than on a horizontal axis as shown in the drawing. In addition, cable .I may be replaced by a net or other engaging means for engaging an aircraft. Also, the static brake-applying cylinder 202 may be positioned radially of reel 14 so that it would be operated by centrifugal force rather than by inertia. Valve 248 may be a ball valve having a ball movable at right angles to a radial line on reel 14 so that centrifugal force would not act on the ball to force it from its seated position. In another arrangement, valve 190 in line 134 from cylinder T may be omitted where the rewind speed is slow enough so that the centrifugal force acting on piston Y is not great enough to cause brake engagement.

While the invention has been described only with reference to a preferred embodiment, it is obvious that modification and alterations will occur to other skilled in the art upon the reading and understanding of this specification.

We claim:

1. A braking device comprising a rotor and a stator, cooperating braking means on said rotor and stator, brake-actuating means on said rotor for engaging said braking means, said brake-actuating'means including a fluid pressure cylinder positioned radially on said rotor, a piston movably positioned in said cylinder, said cylinder having inner and outer ends, a plurality of fluid pressure responsive means, fluid conduit means connecting said outer end of said cylinder with said fluid pressure responsive means, static brake-applying means cooperating with at least one of said fluid pressure responsive means for engaging said braking means when said rotor is at rest, and said piston being movable toward said outer end of said cylinder under influence of centrifugal force when said rotor is rotated to apply pressure to said fluid pressure responsive means when said rotor is rotated.

2. The device of claim 1 wherein said static brake-applying means comprises a second cylinder on said rotor and a second piston in said second cylinder, biasing means biasing said second piston to a position applying fluid pressure to said one fluid pressure responsive means when said rotor is at rest, said piston being movable against said biasing means in response to rotation of said rotor to release pressure from said one fluid pressure responsive means.

3. The device of claim 2 and further including check valve means between said second cylinder and said one fluid pressure responsive means for preventing fluid flow from said cylinder to said one fluid pressure responsive means, and manual bypass valve means around said check valve means.

4. A braking device comprising a rotor and a stator, cooperating braking means on said rotor and stator, brake-actuating means on said rotor for engaging said braking means, said brake-actuating means including brake-engaging means and operating means movably mounted relative to said rotor between brake actuating and deactuating positions, static brake-applying means cooperating with said brake-engaging means for engaging said braking means when said rotor is at rest, and said operating means being movable under influence of centrifugal force from said brake-deactuating position to said brake-actuating position and cooperating with said brakeengaging means for engaging said braking means when said rotor is rotated.

5. The braking device of claim 4 wherein said brake-engaging means includes a plurality of brake-engaging elements, said static brake-applying means cooperating with at least one of said elements and said operating means cooperating with the other of said elements.

6. The device of claim 4 wherein said static brake-applying means is movable relative to said rotor between static brakeengaging and disengaging positions, said static brake-applying means being responsive to rotation of said rotor to move to said brake-disengaging position.

7. A braking device comprising a rotor and a stator, cooperating braking means on said rotor and stator, brake-actuating means on said rotor for engaging said braking means, said brake-actuating means including operating means movably mounted on said rotor for selectively engaging said braking means, said rotor being rotatable in first and second opposite directions, said operating means being movable under influence of centrifugal force when said rotor is rotated in said first direction to engage said braking means, and disabling means for preventing said operating means from engaging said braking means when said rotor is rotated in said second direction.

8. A braking device comprising a rotor and a stator and cooperating braking means on said rotor and stator, static brake-applying means movably mounted on said rotor for movement between brake-engaging position, said static brakeapplying means being biased to said brake-engaging position when said rotor is at rest and being responsive to rotation of said rotor to move to said brake-disengaging position.

9. The device of claim 8 and further including locking means for preventing engagement of said braking means by said static brake-applying means when said static brake-applying means moves to said brake-disengaging position in response to rotation of said rotor. 

1. A braking device comprising a rotor and a stator, cooperating braking means on said rotor and stator, brake-actuating means on said rotor for engaging said braking means, said brake-actuating means including a fluid pressure cylinder positioned radially on said rotor, a piston movably positioned in said cylinder, said cylinder having inner and outer ends, a plurality of fluid pressure responsive means, fluid conduit means connecting said outer end of said cylinder with said fluid pressure responsive means, static brake-applying means cooperating with at least one of said fluid pressure responsive means for engaging said braking means when said rotor is at rest, and said piston being movable toward said outer end of said cylinder under influence of centrifugal force when said rotor is rotated to apply pressure to said fluid pressure responsive means when said rotor is rotated.
 2. The device of claim 1 wherein said static brake-applying means comprises a second cylinder on said rotor and a second piston in said second cylinder, biasing means biasing said second piston to a position applying fluid pressure to said one fluid pressure responsive means when said rotor is at rest, said piston being movable against said biasing means in response to rotation of said rotor to release pressure from said one fluid pressure responsive means.
 3. The device of claim 2 and further including check valve means between said second cylinder and said one fluid pressure responsive means for preventing fluid flow from said cylinder to said one fluid pressure responsive means, and manual bypass valve means around said check valve means.
 4. A braking device comprising a rotor and a stator, cooperating braking means on said rotor and stator, brake-actuating means on said rotor for engaging said braking means, said brake-actuating means including brake-engaging means and operating means movably mounted relative to said rotor between brake actuating and deactuating positions, static brake-applying means cooperating with said brake-engaging means for engaging said braking means when said rotor is at rest, and said operating means being movable under influence of centrifugal force from said brake-deactuating position to said brake-actuating position and cooperating with said brake-engaging means for engaging said braking means when said rotor is rotated.
 5. The braking device of claim 4 wherein said brake-engaging means includes a plurality of brake-engaging elements, said static brake-applying means cooperating with at least one of said elements and said operating means cooperating with the other of said elements.
 6. The device of claim 4 wherein said static brake-applying means is movable relative to said rotor between static brake-engaging and disengaging positions, said static brake-applying means being responsive to rotation of said rotor to move to said brake-disengaging position.
 7. A braking device comprising a rotor and a stator, cooperating braking means on said rotor and stator, brake-actuating means on said rotor for engaging said braking means, said brake-actuating means including operating means movably mounted on said rotor for selectively engaging said braking means, said rotor being rotatable in first and second opposite directions, said operating means being movable under influence of centrifugal force when said rotor is rotated in said first direction to engage said braking means, and disabling means for preventing said operating means from engaging said braking means when said rotor is rotated in said second direction.
 8. A braking device comprising a rotor and a stator and cooperating braking means on said rotor and stator, static brake-applying means movably mounted on said rotor for movement between brake-engaging position, said static brake-applying means being biased to said brake-engaging position when said rotor is at rest and being responsive to rotation of said rotor to move to said brake-disengaging position.
 9. The device of claim 8 and further including locking means for preventing engagement of said braking means by said static brake-applying means when said static brake-applying means moves to said brake-disengaging position in response to rotation of said rotor. 